Time Sieve

Extra turns are usually gated behind a hefty mana cost or a one-shot drawback: this one prices the turn in artifacts instead. Sacrificing five artifacts is a tax most decks can't pay once, let alone repeatedly, which is exactly why the card sat in the toolbox waiting for an engine to make five artifacts a turn cheaply enough to loop it. The combo math is the whole pursuit: pair it with a token producer that floods the board with artifacts (Thopter Foundry and Sword of the Meek became the canonical pairing, manufacturing fodder for the sacrifice and bleeding life away in the process), and the activation stops being a luxury and becomes a recurring loop that takes turn after turn until the game ends. The activation requires a tap, so the extra turns chain only as fast as you can rebuild the five-artifact pile, which is what separates a build that goes infinite from one that just takes one bonus turn and stalls. That dependency is the design's honesty: as a standalone, the rate is unplayable, and the card is content to be. It exists as the payoff half of a two-card machine, the engine that converts a steady stream of disposable artifacts into the most decisive resource in the game. Few cards are so completely defined by what they ask a deck to assemble around them.